1. Field of the Invention
The present invention relates to an image generating apparatus, and more particularly, it relates to an image generating apparatus comprising a rotatable roller for carrying a paper.
2. Description of the Background Art
An image generating apparatus comprising a rotatable roller for carrying a paper is known in general, as disclosed in Japanese Patent Laying-Open Nos. 5-17040 (1993), 8-169574 (1996), 6-106796 (1994), 2004-54169, and 2000-318257, for example. These documents disclose a mechanism allowing transmission of driving force of a motor to a roller in a printing operation and free rotation of the roller in a nonprinting operation (during maintenance of the roller or paper jam).
The image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 5-17040 comprises a rotatable reverse roller (roller), a backing plate fixedly mounted on the reverse roller, a drive gear rotating following driving force of a driving source, a driven gear (roller gear) meshing with the drive gear, a pin for transmitting rotation of the driven gear to the reverse roller, a helical compression spring mounted between the driven gear and the backing plate, a slide lever for sliding the driven gear in a direction of axis of rotation. In the aforementioned Japanese Patent Laying-Open No. 5-17040, the driven gear is slid in a direction to go counter to urging force of the helical compression spring by an operation of the slide lever and the driven gear moves to a position for separating from the drive gear.
The image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 8-169574 comprises an idler gear (drive gear) rotated due to driving force of the driving source, a gear (roller gear) meshing with the idler gear, a paper feed roll shaft mounted with a gear and a paper feed roll (roller), a slidable bearing member, a bearing stop member stopping the bearing member, a spring member urging the bearing member toward the bearing stop member, a lever arranged between the bearing member and the bearing stop member, and two E-shaped rings for regulating an axial position of the paper feed roll. In the aforementioned Japanese Patent Laying-Open No. 8-169574, the bearing member is slid in a direction to separate from the bearing stop member by the lever, thereby releasing a stop state of the bearing member by the bearing stop member. Thus, the paper feed roll shaft can be detached.
The image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 6-106796 comprises a rotatable paper feed roller (roller), a paper feed roller gear (roller gear) mounted on the paper feed roller, a drive motor for driving the paper feed roller gear, a motor gear (drive gear) of the drive motor, a slidable slide gear, a helical compression spring for urging the slide gear in a first direction, and a lever for sliding the slide gear. In the aforementioned Japanese Patent Laying-Open No. 6-106796, the slide gear is slid to a mesh position for meshing with the motor gear and the paper feed roller gear and a separate position for separating the slide gear from the motor gear and the paper feed roller gear by an operation of the lever, thereby switching between a state in which driving force of the drive motor is transmitted to the paper feed roller gear and a state in which the same is not transmitted to the paper feed roller gear.
The image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 2004-54169 comprises a driven gear (drive gear) transmitting driving force of the drive motor, a roller gear mounted on a roller, a slidable slide gear arranged between the driven gear and the roller gear, a spring member urging the slide gear toward the roller gear, and a lever for sliding the slide gear to a mesh position at which the slide gear meshes with both the roller gear and the driven gear and a separate position at which the slide gear meshes with the driven gear only. In the aforementioned Japanese Patent Laying-Open No. 2004-54169, the slide gear is moved to the separate position by the lever, whereby the mesh between the slide gear and the roller gear is released to allow free rotation of the roller.
The image generating apparatus described in the aforementioned Japanese Patent Laying-Open No. 2000-318257 comprises a roller shaft mounted with the platen roller (roller), a roller gear mounted on a first end of the roller shaft, a motor gear (drive gear) transmitting driving force of the motor while meshing with the roller gear, a support portion provided for supporting both ends of the roller shaft and having opening on an upper side, a drop preventing member mounted on a second end of the roller shaft and regulating axial movement of the roller shaft, a hooked member located below the first end of the roller shaft, a lever for swinging the hooked member upward and downward, and a pick-up pin for fixing a position of the lever. In the aforementioned Japanese Patent Laying-Open No. 2000-318257, the hooked member is swung upward by an operation of the lever, thereby lifting the first end of the roller shaft upward. Thus, the mesh between the roller gear and the motor gear is released to allow free rotation of the platen roller. The lever is fixed above the pick-up pin.
In the aforementioned Japanese Patent Laying-Open No. 5-17040, however, the backing plate holding the helical compression spring for urging the driven gear between the compression spring and the driven gear, and the pin capable of moving the driven gear in the axial direction with respect to the shaft and rotating the same together with the shaft are required as a mechanism for switching so as to freely rotate the reverse roller (roller), separately from the reverse roller (roller), the drive gear, the driven gear (roller gear) and the slide lever, whereby the number of components is disadvantageously increased. Additionally, the driven gear is pressed by the helical compression spring and the slide lever in a state where the driven gear is separated from the drive gear, whereby the reverse roller (roller) is disadvantageously difficult to be smoothly rotated.
In the aforementioned Japanese Patent Laying-Open No. 8-169574, the bearing member and the two E-shaped rings are required for regulating the position of the paper feed roll in paper carriage as a mechanism for detaching the paper feed roll separately from the driving source, the idler gear (drive gear), the gear (roller gear) and the lever, whereby the number of components is disadvantageously increased.
In the aforementioned Japanese Patent Laying-Open Nos. 6-106796 and 2004-54169, the slide gear for transmitting or blocking the driving force of the drive motor must be separately provided as a mechanism for switching so as to freely rotate the roller, whereby the number of components is disadvantageously increased.
In the aforementioned Japanese Patent Laying-Open No. 2000-318257, the drop preventing member regulating the axial movement of the roller shaft and the roller gear in paper carriage must be provided as a mechanism for switching so as to freely rotate the platen roller (roller), separately from the roller gear, the motor gear (drive gear) transmitting the driving force of the motor and the lever, whereby the number of components is disadvantageously increased.